\\[-1.8ex] Soil Heterogeneity & $-$0.030 & $-$0.027 & $-$0.031$^{*}$ & $-$0.024 \\ 
  & (0.019) & (0.019) & (0.017) & (0.017) \\ 
\\[-1.8ex] 
Observations & 23,532 & 23,532 & 23,225 & 23,225 \\ 
R$^{2}$ & 0.685 & 0.691 & 0.688 & 0.706 \\ 
